Safety and indicating mechanism for elevators



Jan. 16, 1940. J. c. A. ANDERSON Er AL 2,187,390

SAFETY AND INDICATING MEGHANISM FOR ELEVATORS Filed March 30, 1938 2Sheets-Sheet 1 5w 15, 1940- J. c. A. ANDERSON ET Ax. 2,187,390

SAFETY AND INDICATING MECHANISM FOR ELEVATORS Fild March 5o, 1958 2shams-sheen 2 Patented Jan. `is, 1940 UNITED STATES SAFETY ANDINDICATING MECHANISM i FOR ELEVATOES i John C. A. Anderson and Adolph CG. Anderson, Chicago, lll., assignors to Reliance Elevator ManufacturingCompany, Chicago, lill., a cor poration of Illinois Application March30,

17 Claims.

This invention relates to elevator drives and particularlyto that typeof elevator in which. the elevato-r is supported by a threaded shaft,conimonly called a lifting screw.

A very simple form oi elevator mechanism which eliminatesthe necessityof expensive cable and pulley structure is the type in which theelevator car is supported by a threaded shaft or lifting screw which isrestrained from. rota` tion and which is raised up and down by therotation of a nut having a threaded engagement with the lifting screw,the nut being connected with a pulley whichis driven with belts by asuitable motor mounted on the frame `and housing for the nut and screw.Such a lifting mechanism is extremely simple and because of the self-1locking nature of screws and nuts may be .perfectly Safe as long .as thethreads on the shaft and on the nut remain in good condition., and thisis normally for a period ofmany years. However, in the commercialstructure employed prior to the present invention, there was no way toexamine the driving nut to ascertain the condi tion of the threads, andas a result the threads on such nut cangive way suddenly before the worncondition is discovered, and let the elevator drop because the liftingscrew will pass freely through th-e nut. lThe present invention isconcerned with the positive prevention of any such catastrophe, andwith. providing means to indi-- cate the extent to which the threads ofthe nut may be worn.

Furthermore, in this type of elevator mechanism prior to the present`invention, the lifting 3 screw was normally driven by a Worin or `gearwhich in turn was driven by a motor spaced therefrom and connected tothe worm by a shaft.

In order to stop the movement of the screw as quickly as possible afterthe power was shut 40 off and thus stop the elevator at the desireddoor, a friction brake was applied to the drive shaft. This entiremechanism included a number or" expensive elements, which likewise wereexpensive when they had to be replaced or repaired, and required arelatively large amount of space in the elevator pit. The presentinvention greatly simplies the construction and in addition places thebrake at the safest place, directly on the lifting nut assembly.

According to the present invention both the safety feature andtheindication are provided through the use of a safety .nut whichordinarily bears no load and hence is not appreciably worn, which wouldsupport the shaft in the event that the lifting nut should give way, andwhich is mountedto permit a small amount of vertical movement so thatthe amount of its movement in the course of years will indicate theamount of wear on the threads of the main nut.

The present invention also provides a simpler,

Lil

193s, serial No. 198,835

(o1. 1er- 24o` less expensive and more compact driving mech anisrn witha suitably supported driving nut on the lifting screw with such nutconnected directly with a driving pulley driven by V-type belts from amotor mounted adjacent the pulley in the elevater pit. The pulley isprovided with a flanged portion, having a friction brake thereon whichacts automatically'tc stop the rotation of the pulley upon switching ofithe motor. The brake will be effective even though the driving belt orbelts may break.

The objects ci `the invention are for the moet part apparent from` theforegoing introductory discussion. Further objects and advantages willbe apparent from the following description and from the drawings, inwhich:

jig. l is a fragmentary and partially diagra1nmatic view of an` elevatorsystem. embodying the present invention.

Fig. 2 is a fragmentary sectional view on a larger scale showing oneform of the invention.

3 is a similarlfragmentary sectional view showing a modiiied form of theinvention.

Fig. a is a fragmentary view showing the .or-:aire mechanism on largerscale. v

Although this invention taire numerous forms, only two have been chosenfor illustrat Both. of the illustrated iorms are intended 1Cor use in anelevator system in which the i l raised by a liitingscrew lill.counterbalanced bya weight is in the usual ner. The lifting screwgenerally extends dov .iwardly from the car, through a casing it whichhouses the raising mechanism, and into a tube 5E below the casing it. Y

The mechanism within the casing l includes a motor ll' .provided with acompound pulley lli which through aset of ll-belts l@ drives a pulley 2Hwhich is mounted concentrically with the screw l2 as seen best in Fig.2l is bolted to a nut lill which rota. friction bearings 23 and whichengagement with the screw lf2 so that rot of the nut Ziin one directionthe so ew l2 and in the other direction .lowers the screw l The screw l2is secured to the elevator car li in such a mannerfthat rotation oi hescrew ift is prevented. The car Il .of course runs in Suitable guideswhich prevent its rotation.

` From the foregoing it is seen that driving the motor in. one directiondrives the pulley il and the nut 22 to raise the elevator car, whiledriv ing the motor in the other `directimci in like manner lowers thecar. 1

Because the nut El. is very adequately supported by a pedestal it andbecause it extends for a considerable length along the screw lil, it isobvious that the factor of safety is veryhigh. However, the threads onthe nut f9.2 will Wear so thin in time that the weight of the elevator lThe car nfiay be l thereon, transmitted through the screw I2, will breakthe threads and cause the elevator to drop.

According to the present invention a safety nut 28 is provided, which inthe rst place will give warning of the wear on the threads 21 longbefore they reach their danger point, and in the second place wouldsupport the elevator to prevent its dropping an appreciable distance ifthe threads did fail. It should be understood that the thread of thescrew I2 will not be worn dangerously thin, since the wear correspondingto the wear on the thread 21 is distributed throughout the length of thescrew I 2. Furthermore, even if the thread on the screw I2 did becomeunduly worn, such Wear would be immediately apparent from even a casualinspection. The thread 21, on the other hand, is completely hidden sothat even a careful inspection will not disclose the condition of thesame.

In Fig. 2 the nut 28 is shown as enclosed within a, housing 29 on pulley2|, the housing 29 preferably having a window 3I, which may simply be aremovable plate, to permit inspection of the safety nut 28. The safetynut 28 is caused to rotate with the pulley 2I by a bracket 32 which ispreferably so arranged as to permit the safety nut 28 to move in avertical direction. The safety nut 28 is shaped so that it could come torest on the hub 33 of the pulley 2I, but it is initially positioned asshown in Fig. 2 a substantial distance above the pulley 2I. If thethreads should become worn, they would permit the screw I2 to bepositioned relatively lower in the nut 22, 'and the safety nut 28 wouldlikewise be lowered with the screw I2. A pair of contacts 34 arepreferably provided in a position to be opened by the safety nut 28 soasto break the motor circuit for the motor I1 before the wear on thethreads 21 becomes dangerous. Of course, the contacts 311 could beconnected to operate a danger signal instead of cutting off the motor,Vor a preliminary set of contacts could operate the danger signal and anal set of contacts could cut off the motor in case the wear was longcontinued after the danger signal.

Even if the contacts 34 were not provided or if in the course of yearssome careless engineer should shunt them out of the circuit, there wouldstill be no danger when the safety nut 28 was provided since even thecomplete failure of the threads 21 would merely let the safety nut 28drop onto the seat or hub 33 of the pulley 2l, at which point the safetynut 28 would support the screw I2 and prevent its dropping farther.Inasmuch as the safety nut 28 carries no load but its own weight duringthe many years in which the thread 21 is becoming worn, it is obviousthat the threads of the safety nut 23 will not be appreciably worn. Ofcourse, the contacts 34 could be positioned to extend between thethreads of screw I2 and be actuated by them, but the provision of safetynut I2 is preferred because it absolutely eliminates danger.

' tionship shown.

per and lower thrust bearings are provided and the safety nut 28a is sopositioned that in case the threads 21 should give way, the safety nut28a would be adequately restrained as to both upward or downwardmovement.

In this form ofthe invention the lift screw I2 may be lowered into thepedestal 26a, with the safety nut 28a, the lower thrust bearings 35, aplate 36, the upper thrust bearings 31, nut 22a and ring 33 allassembled thereon in the rela- The sturdy plate 33 may be bolted to thepedestal 26a preferably together with a flange ring 38 which acts as ahousing for the upper thrust bearing` 31. It is thus seen that theweight of the elevator is sustained by the upper thrust bearing 31 whichrests on plate 36, and the weight of the counterweight when it exceedsthat of the elevator is supported by ring 39 and lower bearing 35 whichrests on the underside of plate 36. The ring 39 may be threaded onto thelower end of nut 22a and is locked against unscrewing therefrom by anysuitable key such as a screw 49 screwing into screw 22a through a notchor hole in ring 39.

The form of the invention shown in Fig. 3 is substantially the same inprinciple as that shown in Fig. 2. In this instance the nut may bepositioned at a mid-point in the pedestal 26a so that it may seatdownwardly on the pedestal at 4I or upwardly on the ring 39. It may becaused to rotate with the nut 22 by means of a pin 43 which may bescrewed into the safety nut 28a and may be slidably disposed in a hole Min nut 22a. The contacts 34a may serve the same function' as thecontacts 34 in Fig. 2, to give a warning indication or to shut off themotor, and the contacts 34h may serve the corresponding function in casethe car and its associated parts should be overbalanced. In assemblingthe parts the nut 22a may rst have assembled thereon the bearings 31 and35, plate 33 and ring 39. The ring 39 is preferably then adjusted toprovide the proper bearing action in the frictionless bearings 35 and31, after which the screw 4I) may be inserted. This screw may be anordinary set screw, screwing through the ring 39 if preferred in orderto permit adjustment of ring 39 exactly to any position. Next, the pin43 is inserted in the hole 44 and then the nuts 22a and 28a are screwedonto the lift screw I2, and when they are properly spaced apart thereonthe pin 43 is screwed into the safety nut 28a to retain the nuts 22a and28a in the proper relative position. This entire assembly may then belowered into the pedestal 26a, after which the ring 38 is bolted inplace, and then the drum 2| is bolted to the nut 22a. After the boltshave been applied, the elevato-r car may be secured to the lift screwI2.

The elevator car is secured to the lift screw I2 by means of a plate 56which may be permanently secured onto the lift screw l2 yas by beingthreaded and keyed thereto. The plate 55 is removably secured to theelevator car as by bolts so that' it may be removed from the elevatorcar when desired. To this end the elevator car is of course separatelysecured in place as by being blocked up. When the plate 53 has thus beenremoved from the elevator car, the lift screw I2 may be lowered into thetube I6 and the belts I9 may then be removed and replaced by new belts.

If it should be desired to have some direct reading device forindicating at a glance the amount of wear on the threads 21, this can beareasp@ provided by means of a pointer preferably having its butt endrunning in a groove 46 in safety nut 23a and pivoted as at point 41 nearthe safety nut 28a 'so as to give amplified movement to the needleftllof the pointer. In this structure a scale t@ is provided adjacent theneedle llt, and a cover llpreferably having a glass window is providedfor permitting reading the scale i9 and permitting access 'to the safetynut lilla. It may be noted, incidentally, that the pointer it can extendthrough an opening 53 in the pedestal 26a, which opening can also beused for the insertion ofthe safety nut Eta within the pedestal. Onefeature ofthe invention is the simplified brake system. According tothis feature the brake shoe 6U (including a suitable lining, of course)acts directly on the lifting nut assembly, that is, on liange 5l ofpulley 2l which is secured directly to the nut. This brake shoe may bepivoted to a suitable anchor pin, not shown, carried by the pedestal 2lior Elia and may be actuated in any desirable manner. A very simplemanner of actuation, which is preferred, is that illustrated in Figs. land Ll. A spring Gili normally urges the brake shoe into engagement withthe flange or brake drum` li l. When movement ci the elevator isdesired, i. e., whenever the motor ll is energized, current is suppliedto a solenoid liti. This solenoid may be connected in parallel with themotor I'l or it may be energized by a separate switch simultaneouslytherewith or slightly 1n advance thereof. The solenoid when energized,draws down a rod which in turn draws down a pivoted link t5A carrying aroller at the movable end and pivoted at its other end to a bracket ttcarried by the pedestal 2li or Zta. When the rod 6d is drawn down, thelink G5 approaches the horizontal position and therefore spreads thebrake shoe lill away from the bracket 66 and hence away from the brakedrum lil. When the motor il is turned off under the control of theelevator operator, the current also ceases flowing through solenoid (i3with the result that rod 64 is released and spring t2 presses the brakeshoe Bil into engagement with the brake drum tl. Thetension of thisengagement and hence the rapidity with which the motor l'i and theelevator are brought to a stop is controlled by tighteningnut 6l'` ontension bolt Eil.

It will be observed that this arrangement provides the maximum safetysince not only is the brake shoe applied directly to the lifting nut assembly without `any intervening gears or drive rods which could break,but also the brake is biased in the direction of application rather thanbeing biasedto the off position. Applying the `from the point ofapplication of force and the solenoid connected to be actuated when themotor is turned off. With this construction the solenoid would apply thebrake and the spring would release it'.`

`From the Yforegoing it is seen that means are provided for positivelypreventing accidents due to failure of the threads in the lift screwtype of elevators and for giving some indications and, if

necessary, shutting off the motor before the threads have been wornto'such an extent that their failure is likely to occur. Furthermore, acalibrated scale is provided for indicating the exact amount of wearwhich has occurred on the threads.

Although we have disclosed our invention in its preferred embodiments,it is understood that we do not limit the same thereby, but theinvention is limited only by the scope of the appended claims.

l. .an elevator mechanism including a lift screw, a lift nut rotatablymounted but non-vertically movable .engaging the lift screw, meansforrotating the liftY nut to raise and lower the screw, and asafetynutnormally bearing subN stantiall-y no load but adapted to restrainvertical movement of the screw in the event of failure of the lift nut.

2. An elevator mechanism including a lift screw, a lift nut threadablyengaging the lift screw, means for rotating the lift nut toraise andlower the screw, a safety nut threadably engagingthe screw, rotating ina normally fixed relae tion to said lift nut, and in a normally constanthorizontal path,` but mounted to permit vertical movement, and means forcausing the rotation of the safety nut with the lit nut whereby anywear'on the threads of the lift nut causing the lift screw to change itsrelative threaded position in the lift nut will cause a correspondinglyvertical movement of the safety nut from its original rotary horizontalpath, with said .movement of said safety nut indicating the amount ofwear on the threads of the lift nut.

3; An elevator mechanism including lift screw, a lift nut rotatablymounted but non-vertically movable threadably engaging the lift screw,means for rotating the lift nut to and lower the screw, a safety nutthreadably engaging the screw and normally rotatable in a singlehorizontal path but mounted to permit vertical movement, means forcausing the rotation of the safety nut with the lift nut whereby anyvertical movement of the safety nut will indicate wear on the threads ofthe lift nut, and means for indicating the vertical movement of thesafety nut.

4.-. An elevator mechanism including a lift screw, `a lift nutthreadably engaging the lift screw, means for rotating the lift nut in asubstantially, constant horizontal position to raise and lower thescrew, a safety nut threadably engaging the screw but mounted to permitvertical movement with said screw, means for causing the rotation of thesafety nut with the lift nut whereby any vertical movement of the safetynut will indicate wear on the threads of the lift nut, and electricalcontacts operated by the vertical movement of the safety nut with saidscrew to indicate a predetermined amount of wear on the threads of thelift nut.

5. An elevator mechanism including a lift screw, a lift nut threadablyengaging the lift screw, means for rotating the lift nut to raise andlower the screw, a safety nut threadably engagingY the screw but mountedto permit vertical movement, means for causing the rotation of thesafety nut with the lift nut whereby any vertical movement of the safetynut will indicate wear on the threads of the lift nut, and an indicatorcarried at one end in the safety nut and movable at the other end overan indicating scale, with said indicator operated by the verticalmovellc ment of the safety nut for indicating on the scale the extent ofwear of the threads of the lift nut.

6. An elevator mechanism including a frame, a lift nut threadablysupported by the frame, a pulley secured to the lift nut, means fordriving the pulley to rotate the lift nut, a screw threadably carried bythe lift nut and raised or lowered by its rotation, and a safety nutthreadably carried bythe screw, rotated with the lift nut, and normallysupported by the screw but adapted, in the event of failure of the liftnut, to support the screw at the frame.

7. The combination of an elevator car and an elevator mechanismincluding a lift screw for raising and lowering the car, a lift nutthreadably engaging said screw and rotatable to raise and lower thesame, a safety nut threadably carried by the screw and rotated with thelift nut, and means to limit the movement of the safety nut in eithervertical direction whereby it will limit the elevator car in descendingor ascending movement in the event of failure of the lift nut.

8. An elevator system including an elevator car, a lift screw forraising and lowering the car, a lift nut threadably engaging the screw,a frame for rotatably supporting the lift nut, means for rotating thelift nut to raise or lower the screw and the car, a safety nutthreadably engaging the screw within the frame, and means for causingthe safety nut to rotate with the lift nut, said safety nut beingvertically movable with the screw a limited distance and said frameincluding seat portions adapted to limit the vertical movement of thesafety nut in either direction.

9. An elevator system including an elevator car, a lift screw forraising and lowering the car, a lift nut threadably engaging the screw,a frame for rotatably supporting the lift nut, means for rotating thelift nut to raise or lower the screw and the car, a safety nutthreadably engaging the screw within the frame, means for causing thesafety nut to rotate with the lift nut, said safety nut being verticallymovable with the screw a limited distance and said frame including seatportions adapted `'to limit the vertical movement of the safety nut ineither direction, and contact means adapted to be actuated by the safetynut upon movement in either direction prior to seating on said seatportions for indicating a movement of the safety nut beyond apredetermined amount.

10. An elevator having a platform and an operating mechanism thereforincluding a vertically movable left screw, a pair of nuts engaging thescrew with both nuts being entirely independent of the platform butacting one at a time for supporting the left screw, and means forsupporting the nuts differentially and rotating them simultaneouslywhereby the failure of one nut to support the screw will be evident bydifferential vertical movement of the nuts with the other nutfunctioning as a screw support.

ll. An elevator mechanism including a vertically movable lift screw, afirst support means for said screw and a second support means therefor,each capable of supporting the elevator and lift screw independently ofthe other, and means for differentially supporting said support meanswhereby if one of them fails its failure will be evident from thedifferential movement of the two support means while the other onecontinues to function.

12. An elevator mechanism including a lift member, a fixed supporttherefor, means supported by the support for causing the lift member tolift, and a safety member engaging the lift member, having a normallyidle movement with respect thereto, but adapted to rest on the supportand limit the movement of the lift member if said means fails.

13. A drive mechanism including a drive member, a base, means restingagainst the base to cause the drive member to drive, and a safetir unitengaging the drive member, with a relatively moving relationship Whichis normally relatively idle, but adapted to rest against the base andlimit the movement of the drive member if said means fails.

i4. An elevator mechanism including a lift screw, a lift nut engagingthe lift screw, means for rotating the lift nut in a xed horizontal pathto raise and lower the screw vertically, and indicating meansindependently engaging the threads of the lift screw to indicate adeparture of said threads from their original helical course.

l5. An elevator mechanism including in combination a vertically movablelift screw, a pair of nuts threadably engaging said lift screw with eachof said nuts rotatable normally in a horizontal path, frame means forsupporting said nuts, with one of said nuts being driven to drive thelift screw and non-displaceable vertically, with the other of said nutsbeing displaceable vertically with reference to the one nut and each ofsaid nuts one at a time acting to support the vertically movable liftscrew.

1.6. Lifting mechanism including in combination a vertically movablelift screw, a driven lift nut threadably engaging said lift screw forvertically moving the latter, means for driving said lift nut to rotatethe same, a safety nut threadably engaging said lift screw and rotatablenormally in a horizontal path in a substantially fixed vertical relationwith said lift nut, with said safety nut movable in a vertical directiontoward said lift nut upon failure of the latter for supporting said liftscrew against undesirable downward movement, and frame means forrotatably supporting said lift nut and operatively supporting saidsafety nut when said safety nut is supporting said lift screw.

17. Lifting mechanism including in combination a vertically movable liftscrew, a driven lift nut threadably engaging said lift screw forvertically moving the latter, means for driving said lift nut to rotatethe same, a safety nut threadably engaging said lift screw at a positionvertically displaced from said lift nut and with said safety nut movablein a vertical direction with reference to said lift nut for supportingsaid lift screw against undesirable vertical movement, and frame meansfor rotatably supporting said lift nut having a pair of rigid supportingshoulders on each side of a cavity in said frame means, with said safetynut positioned in said cavity and adapted to engage one supportingshoulder or the other to limit the undesirable vertical movement of saidlift screw.

JOHN C. A. ANDERSON. ADOLPH C. G. ANDERSON.

